Tag Archives: Linux

I’m pleased to announce that today we’re releasing a new snapshot of Cubiquity for Unity. This version finally adds support for both OS X and Linux, and also includes a number of smaller improvements regarding stability, user interface and documentation.

Cubiquity for Unity running on OSX

You can download this latest snapshot using the links below (remember to check our YouTube channel for examples of what Cubiquity for Unity can do):

One of the main appeals of Unity is the ability to target multiple platforms from a single code base, and so we’ve always been keen to bring this functionality to Cubiquity as well. The process is more complex than for other Unity assets because Cubiquity is a native code library written in C++, and so it needs to be compiled (by us) for each platform which we want users to be able to target.

Matt kicked off the work a few weeks ago by compiling Cubiquity for Linux. This involved writing some CMake scripts, testing the process of loading dynamic libraries on Linux, and fixing some OpenGL issues. All of this helped lay the foundations for the OS X version, which then required extra tweaks to the the build process and handling of log files. But eventually it came together 🙂

We haven’t added any significant new features beyond the improved platform support, but there has been more work on polishing the API and particularly on documenting it. The final release will naturally include API docs and a user manual to get you up to speed quickly, but we’re also hoping the API will be simple enough to be intuitive.

We currently expect that this is that last snapshot which we release before we put Cubiquity on the Asset Store! The end is now really in sight and we hope to be live by the end of this month.

Well it’s taken me a few weeks of on and off work but I’ve got Cubiquity working on Linux as a Unity3D add-on. You can try it right now from the Git repository and as long as everything works correctly, it will be available in the next official release.

Cubiquity for Unity3D running on Linux

Porting

There are two essential parts to Cubiquity: the core Cubiquity code where all the magic happens and a thin wrapper providing a C interface to allow easy interaction with Unity’s C♯ code. Cubiquity builds heavily upon PolyVox which has been working on Linux for years now so at least we had a good base to work from. Like PolyVox, Cubiquity is written in C++ which makes it easily portable meaning I had to only make a few trivial changes to the code to get it to build. After a few tweaks to the CMake files, we had a libCubiquityC.so file built and ready.

In order to ease installation and avoid library mismatches, we decided that statically linking all that we could was the best option. Luckily, Cubiquity has few 3rd-party dependencies — in fact it only depends on the C++ standard library and two small Boost libraries. Boost was only being used to fill in features which are now part of C++11 and so by increasing our compiler requirement we could remove the Boost usage entirely. Once here it was simple enough to statically link in libstdc++ and avoid and difficult dynamic library requirements.

For testing purposes, David sent me a simple Unity application which had been exported for Linux and used Cubiquity to create a simple terrain. The idea was that I should be able to place the libCubiquityC.so alongside the executable and the Mono runtime would find the library and load the appropriate stuff from inside it. With a bit of tweaking of the C♯ loading script and recompiling the library as 32-bit (because the Unity app I was using was 32-bit) I was able to run the Unity application and have it render a terrain.

As you can see in that last link, the terrain was not rendering properly and so David set to work getting the shaders working correctly and fighting with some tricky Unity bugs and now it all seems to be working well.

What’s next

Getting Cubiquity working on Linux, as well as being an end in itself, is a useful step towards getting it running on OS X. We are compiling it with both GCC and Clang (which is the OS X compiler) to make sure the code stays portable. In the medium-term we’re working towards being able to easily build the library for all our supported platforms from one place and so I’ve been investigating cross-compiling from Linux to both Windows and OS X. I will give a more detailed description of what I’m doing in a future post but we do already have DLLs and DYLIBs building and they are undergoing testing at the moment. Once we’re confident in the Linux build, we will work on testing out OS X support.

I’ve been hard at work over the last few weeks to iron out some of the main blockers to the Linux port of Voxeliens. One of the major hurdles I’ve been coming up against is the the dangerous area that is ABI compatibility on Linux.

ABI compatibility

For those that don’t know, an ABI (application binary interface) is what allows you to use existing libraries of code in your application, whether they’re things you’re in control of (like our PolyVox library) or system libraries (like glibc or the C++ standard library). For the purposes of the discussion here, an ABI is defined by the symbols that a library contains where symbols are things like functions. As a library evolves over the years they will add functions and each time a release of the library is made with new symbols the library ABI version will increase. Most library developers (and this is particularly true of system libraries like glibc) will promise to never remove any symbols from their libraries which means that an application built against an old version of glibc will still work when run on a new system as all those symbols will still be present (this is called forward compatibility).

The opposite cannot be said to be true. If you build an application on the latest greatest version of your favourite Linux distribution it will freely try to use newer symbols in its dependent libraries. If you then copy that executable to an older distribution and try to run it, it will balk and complain that it can’t find the required symbols. There are tricks one can play to trick the compiler into only using symbols from an old ABI version but the simplest way to achieve the goal is to install an old distribution in a virtual machine and compile all your code there.

This is what I’ve been doing for the past few weeks. I created a VM with a 32 bit installation of openSUSE 11.1 (released December 2008) and have recompiled Voxeliens and all its dependencies in the most minimal way I can. The reason I am doing this in a 32 bit VM rather than a 64 bit one is that 32 bit binaries (technically i686) are compatible with 64 bit operating systems (technically x86_64) whereas the inverse is not true. Ideally these binaries built in the 32 bit VM will work on any Linux OS released in the last 3 or 4 years regardless of whether it’s 32 or 64 bit. This will be one of the main things we’ll need testers for when the time comes.

Bundling libraries

For low level system libraries there’s little choice apart from building against an old version. However, for higher level libraries we have more options. For some libraries with liberal open source licenses we can simply statically link them which essentially involves bundling the library’s code directly into the final executable – thereby avoiding and ABI problems. Any library under a license like the GPL or LGPL, however, cannot legally be statically linked and so the simplest solution here is to include the library file along with the game and tell the executable to use the bundled version rather than any provided by the system.

Shaders are complete

David’s done some excellent work to port all the shaders over to GLSL. In the last update you saw that there was nothing there but flat colours but now everything, including shadows and lighting is working.

What’s left to do?

So now that the building of a portable version of Voxeliens is complete, there’s a few areas that need finishing before it can be released:

Sound. The state of sound output on Linux is a little confusing and not as simple as on Windows. The main problem we’re encountering is that Phonon (the sound API from KDE/Qt), while generally excellent does not provide a sound mixer and so only allows one sound to be played at once. In Voxeliens we often have multiple explosions, laser shots and the music all playing and so we’re investigating using SDL_mixer to mix our sound for us.

There’s still some checks to be done to ensure that the X11 keyboard handling is working as it should be.

Following on from David’s work to port the shaders to GLSL, I’ve been working over the last week or so to get the code compiling for the Linux port. Fortunately Voxeliens is built on top of a number of fantastic open-source projects such as OGRE and Qt which work perfectly on Linux already. As far as our own code, Voxeliens make extensive use of our PolyVox library which I have all along been building and testing on Linux.

Since all our dependencies were working fine, it simply became a case of getting the Voxeliens code itself compiling. This was largely a trivial job, with the bulk of the work involving fixing incorrect case in C++ includes and media files. The largest single change that had to be made was to the keyboard handling. Qt doesn’t provide access to the low level keyboard APIs on Windows or Linux so I had to write some native X11 code to complement the windows.h code we already had.

We still have some work to do on the GLSL shaders to get shadows working and to ensure compatibility with OpenGL 2.1 (since that seems the best target for Linux) and then it’s mostly the work to get it packaged up for distribution across all the different flavours and versions of Linux. Sorting out shared libraries and dependencies is going to be the most amount of work. We’ll be putting out a call for testers once it’s nearer to release to hammer out any problems in this area.

I’ll write up a more technical, in-depth post after the release about the porting process for those who are interested.

This weekend I’ve started the process of getting Voxeliens to run under OpenGL as well as Direct3D. A large part of this transition is handled automatically as we use Ogre as our rendering system and it already has support for both APIs. However, we do need to convert all our HLSL shaders into GLSL versions.

So far this transition is going fairly smoothly, and the screenshot below is taken from the new OpenGL version. As you can see, the voxel colours are coming through but the lighting and shadows are missing. Shadows are probably going to be the trickiest part but hopefully it will come together over the next week of so.

Although I’m still working on Windows, the motivation behind the OpenGL version is to allow the port to Linux. Stay tuned for further updates!

Hello again! Well it’s been a busy couple of weeks but, with the Windows version of Voxeliens finally out of the door, I thought it would be useful to update everyone on our plans for the next couple of months. Getting the game released was a huge milestone but it’s not the end of the project yet 😉

I’ve spent some time over the last week tweaking the payment system. I’ll talk more about this in a future blog post, but basically we wanted a smoother experience. For example, the price displayed now include VAT so there are no more surprises when you reach the checkout stage. We’ve also removed the address and phone number requirements for PayPal orders.

I’m also pleased to announce that we expect to have Voxeliens on GamersGate within the next few weeks. GamersGate contacted us after they saw the initial set of screenshots which we released in December, and I’m currently preparing the material needed to build our product page on their website. Hopefully there will be more news about this in the near future.

After that the priority is the Linux version. Matt will have an important role here as he knows Linux better than I do, but I’m hoping the port won’t be too difficult. We need to port the shaders to GLSL and remove some Windows-specific input code, but we had cross-platform support in mind from the start. We’ll probably also want some Linux testers so stay tuned if you’re interested.

So that’s the immediate plan. There will also be some longer term investment in Voxeliens in terms of getting it onto other distribution sites, running promotional activities, etc, but I expect that in a couple of months we will be able to get back to PolyVox and have a think about our next project.